The present invention concerns a vitreous humor tamponade for the posterior cavity in an eye such as a human eye, in particular for the treatment of retinal detachment.
Relevant state of the art is described in the following literature:
Aronowitz JD and Brubaker RF; Effect of intraocular gas on intraocular pressure; Arch Ophthalmol, 94 (1976) 1191-6;
Cibis PA, Becker B, Okun E and Canaan S; The use of liquid silicone in retinal detachment; Arch Ophthalmol, 68 (1962) 590-9;
Custodis E; Die Behandlung der Netzhautablosung durch umschriebene Diathermiekoagulation und einer mittels Plcmbenaufnaihung erzeugten Eindellung der Sklera im Bereich des Risses; Klin Monatsbl Augenheilkd, 129 (1956) 476-95;
Dimopoulos S and Heimann K; Spatkomplikationen nach Silikonolinjektion. Langzeitbeobachtung an 100 Fallen; Klin Monatsbl Augenheilkd, 189(1986) 223-7;
Freeman WU, Lipson BK, Morgan CM and Liggett PE; New posteriorly located retinal breaks after pneumatic retinopexy; Ophthalmology, 95 (1988) 14-8;
Kanski JJ, Elkington AR and Daavies MS; Diplopia after retinal detachment surgery; AM J Ophthalmol, 76 (1973) 38-40;
Lemmen KD, Dimopoulos S, Kirchhof B and Heimann K; Keratopathy following pars plana vitrectomy with silicone oil filling; Dev Ophthalmol, 13 (1987) 88-98;
Lucke K and Laqua H; Silicone oil in the treatment of complicated retinal detachment; Springer, Berlin, Heidelberg, NY, 1990, 61-6;
Lund OE and Pesch KJ; Uber Fruh- und Spatfolgen nach bulbusumschnurenden Operationen; Ber Dtsch Ophthal Ges, 67 (1965) 202-12;
Machemer R, Buettner H, Norton EWD and Parel JM; Vitrectomy. A pars plana approach; Trans Am Acad Ophthalmol Otolaryngol 75 (1971) 813-20;
Norton EDW; Intraocular gas in the management of selected retinal detachments; Trans Am Ophthalmol Otolaryngol, 77 (1973) 85-98;
Rubin ML; The induction refractive errors by retinal detachment surgery; Trans Am Ophthalmol Soc 73 (1975) 452-90;
Russo CE and Ruiz RS; Silicone sponge rejection. Early and late complications in retinal detachment surgery; Arch Ophthalmol, 85 (1971) 647-50; and
Stinson TW and Donlon JY; Interaction of intraocular air and sulfur hexafluoride with nitron oxide: a computer simulation; Anesthesiology, 56 (1982) 385-8.
Therefore essentially the following procedures are known for the treatment of retinal detachment:
lead seal means or strips are sewn on to the eye. In that way the traction effect which the vitreous humor causes in the region of the hole in the retina is relieved and the foramen itself is tamponned from the outside; and PA1 gases such as SF.sub.6, CF.sub.4, C.sub.2 F.sub.6, C.sub.3 F.sub.8 and inert gases such as krypton or xenon, which are referred to as gas tamponades, or liquids, for example silicone oil, referred to as liquid tamponades, are injected into the vitreous cavity, thereby providing an internal tamponade effect for the hole in the retina.
Those procedures for retinal tamponade involve a number of difficulties which can also be found in the above-indicated literature:
a) The indentation operations are extensive. Large wound areas occur as the conjunctiva has to be opened up and a lead sealing or cerlage bed has to be prepared. The operation requires retrobulbar pain control or intubation narcosis and takes between about 50 and 60 minutes and requires the patient to stay in hospital in a stationary condition for about a week.
In that respect there is the risk of restriction of post-operative eye mobility with consequential double vision (Kanski et al, 1973).
In addition a vision defect such as for example myopia may be induced and increased ( Rubin, 1975).
Circulation of blood to the chorioid is impeded and in addition the chorioid is the point of origin of bleeding into the interior of the eye (Lund, 1965).
The seal or strip material can be rejected, it can suffer from infection and then pierce its way to the outside through the conjunctiva (Russo et al, 1971).
b) The primary gas tamponade is inevitably incomplete as, having regard to the pressure of the eye, only a maximum of one-eighth of the volume of the posterior cavity is tamponned. The patient is required constantly to maintain a head attitude which is often uncomfortable, so that the gas bubble is moved to a position in front of the hole in the retina. For reasons which are unknown at the present time the gas bubble expands to a maximum of double the injected volume (Aronowitz, 1976, Stinsen et al, 1982).
The high degree of mobility of the incomplete tamponade relative to the rest of the vitreous humor, of gel nature, induces vitreo-retinal stresses which in between 10 and 24% of cases induce secondary retinal holes mostly in the lower circumference (Freeman et al, 1988).
c) Tamponade using silicone oil presupposes that firstly the vitreous humor is removed by surgical operation (vitrectomy).
The silicone oil impedes lens nourishment so that a cataract is formed (Dimopoulos et al, 1986).
The silicone oil emulsifies and causes secondary glaucoma (Lucke et al, 1990). A second operation is required to remove silicone oil from the eye again. The silicone oil, when contact occurs, induces irreversible clouding of the cornea (strip degeneration, Lemmen et al, 1987).